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I managed to get 500 miles out of just over a pint after dealing with valve guide seals, a leaking head gasket and putting a restriction between the head and the rocker gear to quell the flow of oil to the valve cover. Was pretty pleased with that given how much oil my car has been known to use, however, yesterday I went for a drive up to Kersey Mill and covered just over 80 miles there and back, approx 40 miles on each leg of the journey.

I checked the oil when I was there after the car had stood for about four hours, oil at max. The leg home, checked again after several hours of standing, I'm down half a pint again.

It's now done about 140 miles since the top up, no use in the first 100 miles or so, half a pint in the last 40..

The route I took was different - on the way up I was on a dual carriageway at a steady 65-70 all the way there, barely any throttle needed. I came back a more scenic route, probably didn't get over 50 all the way, and even then only for a little while.

Running out of reasons to understand why the oil consumption is so unpredictable. Any thoughts from this esteemed font of knowledge? I am wondering if the low speed fuelling is now overly rich and causing oil use under those conditions? The oil is neither on the floor or in the coolant, and the coolant hasn't been 'topping up' the oil either.

Not quite the answer that you want or need Gary but many years ago I learned that when oil is used in a heat machine (which all of our care engines are) then there's only two places that it can go. Into the air via the exhaust or on the floor via a leak! You can't see the first but you can see the second....., on the floor.

I'd put a piece of newspaper under the engine of the car in the garage and then run it until it's warm/up to temp. It'll soon show on the paper of its an oil leak

How have you got your crankcase breathers connected ?

Pcv valve as per Cooper S